A synthesis of the title trisaccharide (14) is reported. The first step of the synthetic route is stereospecific condensation of 2-acetamido-1, 6-anhydro-3-O-benzyl-2-deoxy-β-D-glucopyranose with 2-methyl-(3, 4, 6-tri-O-acetyl-1, 2-dideoxy-α-D-glucopyrano)-[2', 1' : 4, 5]-2-oxazoline to yield a fully protected β-D-(1→4)-linked disaccharide (8) bearing 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) at the non-reducing residue. After acetolysis of the 1, 6-anhydro ring of 8, the resulting fully-protected disaccharide is debenzylated to yield chitobiose heptaacetate (10) having a free hydroxyl group at the C-3 position of the reducing GlcNAc. Compound 10 is glycosylated with 2, 3, 4-tri-O-benzyl-α-L-fucopyranosyl bromide by a bromide ion-catalyzed reaction. After removing the protecting groups of the resulting trisaccharide by debenzylation and de-O-acetylation, an anomeric mixture of 14 is obtained as an amorphous solid. CMR spectral data for 14 are also presented.
                                    本报告介绍了标题三糖 (14) 的合成过程。合成路线的第一步是 2-乙酰
氨基-1,6-脱
水-3-O-苄基-2-脱氧-β-
D-吡喃葡萄糖与 2-甲基-(3,4,6-三-O-乙酰基-1,2-二脱氧-α-
D-吡喃葡萄糖)-[2',1' :4,5]-2-
噁唑啉,从而在非还原残基上生成含有 2-乙酰
氨基-2-脱氧-
D-吡喃葡萄糖(GlcNAc)的完全保护β-D-(1→4)-连接二糖(8)。在对 8 的 1,6-脱氢环进行乙酰分解后,得到的完全受保护的二糖被去苄基化,生成壳
寡糖庚
乙酸酯(10),其还原型 GlcNAc 的 C-3 位上有一个游离羟基。化合物 10 通过
溴离子催化反应与 2,3,4-三-O-苄基-α-L-
吡喃
核糖基
溴化物糖基化。通过去苄基化和去 O-乙酰基化去除所得三糖的保护基团后,得到无定形固体 14 的同分异构体混合物。文中还提供了 14 的 CMR 光谱数据。